Many portable devices, for example mobile telephones, are equipped with a display such as a glass or plastic display window for providing information to the user. Furthermore such display windows are now commonly used as touch sensitive inputs. The use of a touch sensitive input with the display has the advantage over a mechanical keypad in that the display may be configured to show a range of different inputs depending on the operating mode of the device. For example, in a first mode of operation the display may be enabled to enter a phone number by displaying a simple numeric keypad arrangement and in a second mode the display may be enabled for text input by displaying an alphanumeric display configuration such as a simulated Qwerty keyboard display arrangement.
However such touchscreen inputs have a disadvantage with respect to mechanical keys in that the user does not experience the usual expected click or mechanical switch feedback to indicate that an input has been detected. To attempt to overcome this some equipment has been provided with a mechanical or audible simulation of a key press. Some touch screen devices are equipped with device haptic feedback, in other words an ordinary vibration is used to make the whole device shake (and also provide an audio cue of the key press) as the user touches the screen and is detected. These device-haptic devices however are themselves problematic as they require significant current to operate in order to generate significant feedback force. This is generally because the construction of the device often requires that the front window is firmly located or fixed to the surrounding frame or connected in such a way to significantly damp the force generated by the actuator before it is applied.
Furthermore some devices use electro-acoustic transducers to produce audio for earpiece and integrated hands free (IHF) operations as well as for alert tones. The moving coil dynamic speaker configuration used is typically relatively large in relation to the volume within the device and require specific signal processing considerations in order that the acoustic frequency response is acceptable. Furthermore moving coil transducers can attract contaminants such as small iron particles from within the internal volume of the device and also through ports provided to enable acoustic wave transmission from the speaker to the external environment. These contaminants can cause distortion and faults within the speakers significantly reducing the lifetime of the device.
Therefore a typical device configured to produce both audio and haptic outputs would typically require a vibrator component and an electro-acoustic transducer which incurs both cost of component, and also volume cost as they are relatively difficult to fit into a modern device and need to be located far from the mass centric point in order to generate a good performance. Furthermore in devices generating a multi-channel audio signal these modern devices require additional volume and component cost as additional transducers are required to generate each of the audio channels.